Principles and practices for biodiversity conservation and restoration forestry: a 30 year case study on the Victorian montane ash forests and the critically endangered Leadbeater’s Possum

We present a detailed case study of conservation and restoration of the Australian arboreal marsupial Leadbeater’s Possum (Gymnobelideus leadbeateri) and its Mountain Ash forest habitat to illustrate the important intersection between forest restoration principles and the general principles for forest biodiversity conservation. Mountain Ash forests have been extensively modified through a century of intensive logging, recurrent wildfires and post-fire salvage logging. These disturbances have led to a reduction in old growth forest to 1/30th-1/60th of the extent of historical levels, a rapid collapse followed by a prolonged (>30-year) shortage of populations of hollow-bearing trees throughout the Mountain Ash forests (which are critical habitat elements for many species of cavity-dependent vertebrates), and an increased risk of re-burning of landscapes dominated by young, regrowth forest.The consequences of the severe decline and consequent ‘temporary extinction’ of large old trees will be the potential global extinction of Leadbeater’s Possum whose distribution is significantly associated with the number of large old trees.We outline the conservation and forest restoration principles and practices that are needed to address these problems.We discuss how general principles for forest restoration must be multi-faceted and multi-scaled by encompassing strategies ranging from retaining existing key residual elements of original natural forest cover (e.g. remaining populations of target species, key structures, habitats, and patches) through to restoring patterns of forest cover and key ecosystem processes.We also outline how forest restoration principles intersect strongly with similarly multi-faceted and multi- scaled general principles for forest biodiversity conservation – in particular, those corresponding to conserving populations of particular species and their habitats, maintaining stand structural complexity, maintaining patterns of landscape heterogeneity, and perpetuating key ecosystem processes. Finally, we outline the potential for positive cumulative benefits of multiple restoration and conservation strategies by outlining how actions at one scale can create benefits at other (smaller or larger) scales.

Fire severity and landscape context effects on arboreal marsupials

Although fire is a major form of natural disturbance worldwide, both fire-derived landscape context effects and the impacts of fire severity are poorly known for many species. To address this knowledge gap, we quantified the response of Australian arboreal marsupials to: (1) the spatial effects of fire, (2) fire severity, and (3) fire impacts on the availability of critical nesting resources – hollow-bearing trees.

We identified substantial differences among species in response to fire severity and landscape-scale fire. The Sugar Glider (Petaurus breviceps) and the endangered Leadbeater’s Possum (Gymnobelideus leadbeateri) were extremely rare on burned sites irrespective of fire severity. In addition, these two species declined with the amount of burned forest in the surrounding landscape even when their habitat remained unburnt. The Mountain Brushtail Possum (Trichosurus cunninghami) and the Greater Glider (Petauroides volans) both occurred on burned and unburned sites. The Greater Glider responded nega- tively to fire severity at the site level and also negatively to the amount of forest burned in the surrounding landscape. The abundance of the Mountain Brushtail Possum was lowest on sites subject to moderate severity fire.

On unburned sites, the presence and abundance of virtually all species was characterised by a common positive response to the availability of nesting resources in hollow-bearing trees.

Our findings underscore the importance of management practices to better protect species that decline after fire. These include conserving areas of unburned forest, particularly those with hollow-bearing trees which are critical nest sites for arboreal marsupials. These recommendations are currently the opposite of existing management practices.

Senate Inquiry Report: Effectiveness of threatened species and ecological communities’ protection in Australia